Fracture Risk Rises after Gastric Bypass Surgery

This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson. 

Nearly 200,000 Americans have bariatric surgery each year, so it’s important to understand the long-term musculoskeletal consequences of those procedures. Gastric bypass constitutes the most common bariatric surgery and is believed to lead to bone loss. However, fracture risk in gastric-bypass patients has been insufficiently studied. Given that diabetes is an independent risk factor for fractures, any gastric bypass–fracture association should be studied in patients with and without diabetes.

That’s what Swedish researchers did in a retrospective cohort study¹ of 38,971 obese patients who underwent gastric bypass—7,758 of whom had diabetes and 31,213 of whom did not. The patients in each of the two groups were propensity-score matched with controls (1 to 1). The researchers evaluated the overall risk of fracture and fall injury, along with fracture risk according to amount of weight loss and degree of calcium and vitamin D supplementation during the first year after surgery.

After a median follow-up of 3.1 years, gastric bypass was associated with an increased risk of any fracture, both in patients with diabetes (HR, 1.26) and without diabetes (HR, 1.32). Fracture risk appeared to increase with time. The risk of fall injury without fracture also increased after gastric bypass. (The increased risk of fall injury may explain some of the increased fracture risk.) Surprisingly, neither higher amounts of weight loss nor poor calcium and vitamin D supplementation during the first year after surgery were associated with increased fracture risk.

The metabolic consequences of surgically induced weight loss are significant for the obese population. Those consequences probably reach beyond bone to affect many aspects of musculoskeletal and possibly neurological homeostasis.

Reference

1. Axelsson KF, Werling M, Eliasson B, Szabo E, Näslund I, Wedel H, Lundh D, Lorentzon M. Fracture Risk After Gastric Bypass Surgery: A Retrospective Cohort Study. J Bone Miner Res. 2018 Jul 16. doi: 10.1002/jbmr.3553. [Epub ahead of print] PMID: 30011091